Abstract
Tuning the optoelectronic properties of donor-acceptor conjugated polymers (D-A CPs) is of great importance in designing various organic optoelectronic devices. However, there remains a critical challenge in precise control of bandgap through synthetic approach, since the chain conformation also affects molecular orbital energy levels. Here, D-A CPs with different acceptor units are explored that show an opposite trend in energy band gaps with the increasing length of oligothiophene donor units. By investigating their chain conformation and molecular orbital energy, it is found that the molecular orbital energy alignment between donor and acceptor units plays a crucial role in dictating the final optical bandgap of D-A CPs. For polymers with staggered orbital energy alignment, the higher HOMO with increasing oligothiophene length leads to a narrowing of the optical bandgap despite decreased chain rigidity. On the other hand, for polymers with sandwiched orbital energy alignment, the increased band gap with increasing oligothiophene length originates from the reduction of bandwidth due to more localized charge density distribution. Thus, this work provides a molecular understanding of the role of backbone building blocks on the chain conformation and bandgaps of D-A CPs for organic optoelectronic devices through the conformation design and segment orbital energy alignment.
| Original language | English |
|---|---|
| Article number | 2302178 |
| Journal | Advanced Materials |
| Volume | 35 |
| Issue number | 41 |
| DOIs | |
| State | Published - Oct 12 2023 |
Funding
This work was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Science under award number of DE‐SC0022050. Z.L., S.A.T., and W.X. acknowledge support from the U.S. National Science Foundation under NSF OIA Award No. 2119691. S.R.‐G. thanks the Natural Sciences and Engineering Research Council of Canada (NSERC) for support through a Discovery Grants (RGPIN‐2022‐04428). G.M.T. thanks the Government of Ontario for support through an Ontario Graduate Scholarship. This research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. Part of the research was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. The authors thank Kunlun Hong (CNMS) for assistance during the neutron scattering experiments. This work was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Science under award number of DE-SC0022050. Z.L., S.A.T., and W.X. acknowledge support from the U.S. National Science Foundation under NSF OIA Award No. 2119691. S.R.-G. thanks the Natural Sciences and Engineering Research Council of Canada (NSERC) for support through a Discovery Grants (RGPIN-2022-04428). G.M.T. thanks the Government of Ontario for support through an Ontario Graduate Scholarship. This research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. Part of the research was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. The authors thank Kunlun Hong (CNMS) for assistance during the neutron scattering experiments.
Keywords
- backbone planarity
- chain conformation
- donor-acceptor (D-A) conjugated polymers
- optoelectronic properties
- orbital energy alignment
- small-angle neutron scattering (SANS)